You cannot modify the redundancy level of a disk group once it has been created. It is mentioned in the documentation. You can only backup your data and create a new disk group or move the data to another disk group.

Say I move from external redundancy +OCRVOTE diskgroup to normal redundancy +CRS diskgroup. And then I drop the diskgroup +OCRVOTE, and recreate it with normal redundancy. And then move from _CRS to +OCRVOTE. Is that possible?

Step 1: Create diskgroup +CRS with normal redundancy

Step 2: Move from the diskgroup +OCRVOTE which is with external redundancy to +CRS diskgroup

These steps will work these are the same steps I took took to move the OCR to a normal redundancy disk group. One thing you need to check is where the spfile of the ASM instance is located if you are using the spfile. Normally the spfile for the ASM instance is create in the same diskgroup were the OCR is created.

Below are my steps

as root

/oragridbase/product/11.2.0/grid/bin/ocrconfig -showbackup

/oragridbase/product/11.2.0/grid/bin/ocrcheck

/oragridbase/product/11.2.0/grid/bin/ocrconfig -add +DG_OCR_VOTEDISK

/oragridbase/product/11.2.0/grid/bin/ocrcheck

/oragridbase/product/11.2.0/grid/bin/ocrconfig -delete +DG_OCR_VOTE

/oragridbase/product/11.2.0/grid/bin/ocrcheck

If you are moving your OCR to normal redundancy diskgroup you should do the same for your vote as well.

You need to look at the other replies in your post. One thing you need to make sure your vote disk are not in the same diakgroup you are planning to recreate is so you need to move the vote as well. Look at the reply Levi posted.

Yes it is OK but you need to make sure the VOTE and the ASM instance SPFILE is not in the same existing diskgroup that you want to drop and recreate. It does not matter the redundancy type for the diskgroup you are moving to for the OCR or the SPFILE. Below is the complete steps I took to move my OCR, VOTE and SPFILE to a normal redundancy diskgroup. I would check where you have the vote by executing crsctl query css votedisk. To check the spfile for the asm instance login to the asm instance and do show parameter spfile.

--Note: all this is done online

/oragridbase/product/11.2.0/grid/bin/ocrconfig -showbackup

/oragridbase/product/11.2.0/grid/bin/ocrcheck

/oragridbase/product/11.2.0/grid/bin/ocrconfig -add +DG_OCR_VOTEDISK

/oragridbase/product/11.2.0/grid/bin/ocrcheck

/oragridbase/product/11.2.0/grid/bin/ocrconfig -delete +DG_OCR_VOTE

/oragridbase/product/11.2.0/grid/bin/ocrcheck

--Note: all this is done online

--Move vote with Normal redundancy you need at least 3 failover groups for the vote